A unified damage and fracture model,the combinatory work density model,which is suitable for ei- ther non-cracked body or cracked body has been suggested.In the present paper,the deformation and fracture of the two ki...A unified damage and fracture model,the combinatory work density model,which is suitable for ei- ther non-cracked body or cracked body has been suggested.In the present paper,the deformation and fracture of the two kinds of tensile spceimen and TPB specimen made of 40Cr steel have been simulated by using the new mod- el together with the large èlastic-plastic deformation finite element method.The results give a good picture of the whole deformation and fracture processes of the specimens in experiments;especially,the results on the TPB specimen can be used to obtain the relationship between load and displacement at the loading point P-Δ,and between crack ex- tension and displacement at the loading point Δα-Δ,the resistance curve J_R-Δa and the fracture toughness J_(IC).All the results are in remarkable agreement with those obtained by experiments.Therefore the model suggested here can be used to simulate crack initiation and propagation in non-cracked body and fracture initiation and crack stable propa- gation in cracked body.展开更多
Based on experimental restilts of brittle, intact sandstone under uniaxial compression, the micro-parameters were firstly confirmed by adopting particle flow code （PFC2D）. Then, the validation of the simulated model...Based on experimental restilts of brittle, intact sandstone under uniaxial compression, the micro-parameters were firstly confirmed by adopting particle flow code （PFC2D）. Then, the validation of the simulated models were cross checked with the experimental results of brittle sandstone containing three parallel fissures under uniaxial compression. The simulated results agreed very well with the experimental results, including the peak strength, peak axial strain, and ultimate failure mode. Using the same micro- parameters, the numerical models containing a new geometry of three fissures are constructed to investigate the fissure angle on the fracture mechanical behavior of brittle sandstone under uniaxial compression. The strength and deformation parameters of brittle sandstone containing new three fissures are dependent to the fissure angle. With the increase of the fis- sure angle, the elastic modulus, the crack damage threshold, and the peak strength of brittle sandstone containing three fissures firstly increase and secondly decrease. But the peak axial strain is nonlinearly related to the fissure angle. In the entire process of deformation, the crack initiation and propagation behavior of brittle sandstone containing three fissures under uniaxial compression are investigated with respect to the fissure angle. Six different crack coalescence modes are identified for brittle sandstone containing three fissures under uniaxial compression. The influence of the fissure angle on the length of crack propagation and crack coalescence stress is evaluated. These investigated conclusions are very important for ensuring the stability and safety of rock engineering with intermittent structures.展开更多
The fatigue crack initiation from notch root and the short-crack growth laws of two medium carbon alloying structural steels—35CrMo and 42CrMo are investigated under the different stress ratios R =0.1, 0.3) and th...The fatigue crack initiation from notch root and the short-crack growth laws of two medium carbon alloying structural steels—35CrMo and 42CrMo are investigated under the different stress ratios R =0.1, 0.3) and three-point bending condition. The relationships between the maximum stress range at the notch root Δ σ max and the number of cycles before fatigue crack initiation N i are determined. The threshold stresses of fatigue crack initiation (Δ σ max ) th are got, and the smallcrack growth laws are obtained for these steels. An effective and convenient method is proposed for predicting the fatigue life of the notch specimens.展开更多
基金The project supported by National Natural Science Foundation of China
文摘A unified damage and fracture model,the combinatory work density model,which is suitable for ei- ther non-cracked body or cracked body has been suggested.In the present paper,the deformation and fracture of the two kinds of tensile spceimen and TPB specimen made of 40Cr steel have been simulated by using the new mod- el together with the large èlastic-plastic deformation finite element method.The results give a good picture of the whole deformation and fracture processes of the specimens in experiments;especially,the results on the TPB specimen can be used to obtain the relationship between load and displacement at the loading point P-Δ,and between crack ex- tension and displacement at the loading point Δα-Δ,the resistance curve J_R-Δa and the fracture toughness J_(IC).All the results are in remarkable agreement with those obtained by experiments.Therefore the model suggested here can be used to simulate crack initiation and propagation in non-cracked body and fracture initiation and crack stable propa- gation in cracked body.
基金supported by the Fundamental Research Funds for the Central Universities (China University of Mining and Technology) (Grant 2014YC10)the National Basic Research 973 Program of China (Grant 2014CB046905)
文摘Based on experimental restilts of brittle, intact sandstone under uniaxial compression, the micro-parameters were firstly confirmed by adopting particle flow code （PFC2D）. Then, the validation of the simulated models were cross checked with the experimental results of brittle sandstone containing three parallel fissures under uniaxial compression. The simulated results agreed very well with the experimental results, including the peak strength, peak axial strain, and ultimate failure mode. Using the same micro- parameters, the numerical models containing a new geometry of three fissures are constructed to investigate the fissure angle on the fracture mechanical behavior of brittle sandstone under uniaxial compression. The strength and deformation parameters of brittle sandstone containing new three fissures are dependent to the fissure angle. With the increase of the fis- sure angle, the elastic modulus, the crack damage threshold, and the peak strength of brittle sandstone containing three fissures firstly increase and secondly decrease. But the peak axial strain is nonlinearly related to the fissure angle. In the entire process of deformation, the crack initiation and propagation behavior of brittle sandstone containing three fissures under uniaxial compression are investigated with respect to the fissure angle. Six different crack coalescence modes are identified for brittle sandstone containing three fissures under uniaxial compression. The influence of the fissure angle on the length of crack propagation and crack coalescence stress is evaluated. These investigated conclusions are very important for ensuring the stability and safety of rock engineering with intermittent structures.
文摘The fatigue crack initiation from notch root and the short-crack growth laws of two medium carbon alloying structural steels—35CrMo and 42CrMo are investigated under the different stress ratios R =0.1, 0.3) and three-point bending condition. The relationships between the maximum stress range at the notch root Δ σ max and the number of cycles before fatigue crack initiation N i are determined. The threshold stresses of fatigue crack initiation (Δ σ max ) th are got, and the smallcrack growth laws are obtained for these steels. An effective and convenient method is proposed for predicting the fatigue life of the notch specimens.
